Conveyor belt and system with a non-collapsing inside edge

ABSTRACT

A conveyor belt and conveying system designed to operate about lateral curves is disclosed. The conveyor belt is comprised of transverse rods interconnected by links disposed along opposite transverse edges of the belt. When the belt proceeds about a lateral curve, the pitch along the inside edge of the curve is kept substantially the same as in straight line motion, while the outside edge of the belt is allowed to expand to a second greater pitch. In one embodiment support links are disposed along the inside edge of the belt and provide support for the inside edge of successive tiers of the belt as the belt travels a helical path. A specific link construction which uses a worked hardened bearing surface is also disclosed.

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.171,390, filed on Mar. 21, 1988, U.S. Pat. No. 4,867,301, which in turnis a continuation-in-part of application Ser. No. 083,272 abandoned,filed Aug. 10, 1987, and a continuation-in-part of application Ser. No.213,171 filed on Jun. 29, 1988, which in turn is a continuation-in-partof application Ser. Nos. 083,272 abandoned, and 171,390.

TECHNICAL FIELD

This invention relates to a conveyor belt and system designed to travelabout lateral curves. More specifically, the invention concerns aconveyor belt which includes tranverse rods connected by links disposedalong the opposite transverse ends of the rods, wherein the inside endsof the rods along the inside edge of the belt are kept at a constantfirst pitch and the outside ends of the rods are allowed to move to asecond larger pitch.

BACKGROUND OF THE INVENTION

Conveyor belts comprised of transverse rods connected by links disposedalong the opposite transverse edges of the belt have been in use for along period of time. One such prior art belt uses generally U-shapednestable links with slotted holes that allow the links to slide on therods. The relative sliding action betwen the links and rods provideslateral flexibility which enables the belt to turn right or left, whensuch nestable links are used on both sides of the belt. When such a beltproceeds around a lateral curve, the rod ends along the inside concaveedge of the belt collapse. The opposite transverse ends of the rodsalong the outside convex edge of the belt either remain at the samepitch as when the belt travels in a straight line direction, such asdisclosed in U.S. Pat. No. 3,225,898 to Roinestad, or expand to agreater pitch in order to allow the belt to proceed around a smallerradius, as disclosed in U.S. Pat. No. 4,078,655 to Roinestad.

The collapsing or diminshing pitch of the belt along the inside edge ofa lateral curve cretes several problems. First of all, most ware ischarged into a conveying system in a rank and file arrangement, andspacing of the ranks (crosswise rows) can only be controlled byadjusting the relative speeds of the individual feed conveyors. To makecertain that the ware does not overlap, it is necessary to take intoaccount the collapsing pitch and to also leave a safety margin in thespacing, both of which result in a drop in efficiency. If the ware beingconveyed is soft in nature, the collapsing pitch can result in wrinklingof the ware. Also, if the conveyor is used in a freezing plant, thecollapsing pitch can result in contact and freezing together of adjacentware if sufficient spacing is not used.

U.S. Pat. No. 4,662,509 issued to Kaak on May 5, 1987 addresses theproblem of a conveyor belt having a collapsing inner edge in a chaintype conveyor belt wherein the ware support carriers are connecteddirectly to a drive chain. The chain conveyor belt in the '509 patentuses triangular carriers consisting of a rod-shaped element and apulling element. Along the inside edge of the conveyor belt, therod-shaped element and the pulling element are pivotably connected tothe drive chain, and the pitch of the rod-shaped elements is heldconstant by the connection to the drive chain. The pulling elementsslant backward in the direction of travel of the belt and are pivotablyconnected to one of the rod-shaped elements further rearward along thebelt. As the belt proceeds around a curve, the outside, free ends of therod-shaped elements increase their spacing or pitch with respect to oneanother.

The conveyor belt disclosed in the '509 patent, however, has certaindisadvantages or limitations. The triangular configuration of the warecarriers precludes negotiation about end pulleys or rolls, or operatingthrough a verticle hanging take-up mechanism. The practical width of theware carriers is limited by the triangular configuration, because theeffectiveness of the pulling element diminishes with increasing width.Finally, the overlapping orientation of the pulling and rod-shapedelements gives rise to serious sanitation difficulties. The capabilityto clean between all elements of a belt is important when the conveyorbelt is used in a food handling environment.

It has also been discovered that the use of a link mechanism which keepsthe inside rod ends at a constant pitch along the inner concave edge ofa belt, both with dual pitch links and with nestable U-shaped outsidelinks is particularly suitable for use in a conveying system wherein thebelt travels along a helical path with the belt being arranged in anumber of superimposed helically extending tiers. Prior art helical tiersystems, such as disclosed in U.S. Pat. Nos. 3,348,659 and 4,078,655 toGerald C. Roinestad have used conveying belts with a collapsing inneredge. The successive tiers of belt in the '659 and '655 patents aresupported by a support frame separate from the belt. The minimum tierheight in such a system is equal to the sum of the heights of theseparate belt support frame, the ware being conveyed and the belt,resulting in a system with a relatively large vertical extent. U.S. Pat.No. 3,938,651 to Alfred et al. discloses a conveying system forconveying in a helical path wherein the belt is self-supporting alongboth the inner and outer edges of the belt.

Another aspect of the invention is directed to the construction of theU-shaped links, particularly the construction of the portion connectingthe legs of the link. It has been known in the prior art to curve thebearing surface of the connecting portion of U-shaped links. Forexample, the bearing surface of certain pintel chain links manufacuredby the Allied-Locke Industries, Incorporated are curved. However, suchprior art curved bearing surfaces for tractive links do notsubstantially increase the wear characteristics of the links in themanner of the present invention.

SUMMARY OF THE INVENTION

The present invention is directed to a conveyor belt for conveyingaround lateral curves. The lateral curves have a predetermined maximumcurvature with a predetermined radius of curvature. The belt iscomprised of a plurality of rods and a mechanism for connecting the rodsto form a length of belt. The rods extend transversely of the length ofthe belt between an inside end along the inside edge of the lateralcurves and an outside end along the outside edge of the lateral curves.The rods are arranged adjacent one another along the length of the belt.The connecting mechanism includes a link mechanism disposed adjacent theinside and outside ends of the rods for coupling adjacent pairs of rodsto one another. The link mechanism also keeps the inside and outsideends of the rods at substantially the same pitch during straight linemotion of the belt. During motion of the belt about a lateral curve, thelink mechanism keeps the inside ends of the rods at the first pitch andallows the outside ends of the rods to move to a second greater pitch asthe belt moves from straight line to lateral curved motion and to returnto the first pitch as the belt moves from the lateral curved to straightline motion. The link mechanism includes, along the inside concave edgeof the belt, a plurality of separate inside links joining each pair ofadjacent rods and, along the outside convex edge of the belt, at leastone outside link joining each pair of adjacent rods. Each of the outsidelinks has holes through which the rods extend including at least oneslot to allow the outside ends of the rods to move to the second pitch.Each of the inside links includes holes having end surfaces spaced apredetermined distance such that a plurality of the inside links joiningadjacent rods aligns the adjacent rods in a generally parallel relationat the first pitch when the belt is under tractive load in straight lineconveying motion.

In a preferred embodiment of the invention, the inside links include atleast two generally U-shaped links joining adjacent pairs of the rods,and the outside links include at least one link joining adjacent parisof the rods. Each of the U-shaped links has a pair of spaced legportions extending generally in the lengthwise dimension of the belt anda connecting portion joining the spaced leg portions. Each of the legportions has holes formed through it for the passage of an adjacent pairof rods. The holes in the leg portions of the inside links and in theoutside links have end surfaces with predetermined longitudinal spacingbetween the end surfaces. The holes in the inside links have a firstlongitudinal end surface spacing, while the holes in the outside linkshave a second, greater longitudinal end surface spacing. The firstlongitudinal spacing is correlated to the second longitudinal spacingand to the predetermined radius of the curvature so that in straightline conveying motion the inside ends of the rods are kept at the firstpitch and the inside U-shaped links are tractive while the outisde linksare non-tractive, and during lateral curved conveying motion the insideends of the rods are kept at substantially the first pitch and at leastone of the inside U-shaped links remains tractive while the outside endsof the rods move to the second greater pitch.

The correlation of the longitudinal spacing of the end surfaces ispreferably set so that the outside ends of the rods contact the opposingend surfaces of the holes in the outside links when the belt travelsaround a lateral curve of the predetermined maximum curvature with theoutside links assuming only a minimal amount of tractive load. Such acorrelation assures that at least one of the inside links remainstractive and that the inside ends of the rods remain at substantiallythe first pitch. The use of this correlated spacing is particularlyadvantageous in a helical tiered conveying system wherein the curvaturein the helix is the maximum curvature of the system. The belt can thenbe readily adapted to the system so that a non-collapsing inside edge isassured throughout the tiers of the system, while the outside edge ofthe belt moving through the tiers is stabilized by the contact of therods with the end surface of the holes in the outside links.

Another embodiment of the link mechanism also holds the first and secondtransverse ends of the rods at substantially the same first pitch duringstraight line motion of the belt, and during motion of the belt about alateral curve, this link mechanism holds the rods to the first pitchalong the transverse ends of the rods located at the inside concave edgeof the lateral curve. However, this link mechanism moves the oppositetransverse ends of the rods to a second greater pitch along the outsideconvex edge of the lateral curve as the belt proceeds from straight lineto lateral curved motion, and returns the opposite transverse ends ofthe rods to the first pitch as the belt moves from lateral curved tostraight line motion.

The conveyor belt using the second embodiment of the link mechanism canbe adapted to travel around lateral curves in a single direction oraround lateral curves in both the right and left directions. When thebelt is designed to travel around lateral curves in a single direction,the link mechanism includes both single pitch links and dual pitchlinks. However, when the belt is designed to travel around lateralcurves in both the left and right directions, dual pitch links aredisposed along both edges of the belt. The dual pitch links arepivotable between a first position and a second position. In the firstposition the transverse ends of the rods connected by the respectivelinks are held at the first pitch; and, during the pivoting motion ofthe links from the first to the second position, are moved from thefirst pitch to the second pitch.

Each of the dual pitch links includes a body which has a pivot apertureand a pitch changing slot. The transverse end of one of the rods isreceived in the pivot aperture and the transverse end of an adjacent oneof the rods is slidably received in the pitch changing slot. A cammechanism is provided for pivoting the dual pitch links between theirfirst and second positions during motion around lateral curves.

A conveyor belt formed of the transverse rods and dual pitch links, orlinks which allow the outside edge of the belt to expand while keepingthe inside edge of the belt at a constant pitch, allows the belt tooperate in a straight line direction and around curves without theproblems resulting from a conveyor belt that has a collapsing inner edgeas it proceeds around lateral curves.

Another preferred aspect of the present invention is directed to the useof at least one support link joining pairs of the adjacent rods. Thesupport links include a longitudinal portion extending bothlongitudinally between a pair of the adjacent rods and vertically awayfrom the rods, and at least one tab portion extending transversely fromthe longitudinal portion. Holes are formed in each longitudinal portionto couple the support links to adjacent pairs of rods. The tab portionsare spaced a predetermined vertical distance from the rods to contact aninside edge of an adjacent vertically spaced tier of the belt andthereby support the inside edge of the superimposed tiers when the beltis arranged to travel along a helical conveying path.

The present invention is also directed to a conveying system which usesbelts of the type described and which moves the belt through a helicalconveying path that forms a plurality of stacked tiers of the belt.Belts which have a constant non-collapsing inside pitch are particularlyuseful in such stacked tier systems since a significantly less amount ofbelt is required for a given helical path over the amount of belt whichis needed using prior art belts with a collapsing inside edge. Lessamount of the belt is necessary to accommodate the same amount of anoffloading surface. The use of a non-collapsing pitch in combinationwith a drive drum and support links along the inside edge of the belt isparticularly advantageous, because localized shifting of the inside edgeof the belt as it moves through the helical path is greatly minimized.

A further preferred aspect of the present invention is directed to theconstruction of the U-shaped links in a manner to substantially increasetheir wear characteristics. According to this aspect of the invention,tractive link members for connecting adjacent rods of an endlessconveyor belt are comprised of a substantially flat piece of metal whichis formed into a general U-shape with a pair of spaced leg portionsjoined by a connecting portion. The substantially flat piece of metalhas a reduced thickness area in the connecting portion formed of acompressed, work-hardened area of the metal. The work-hardened area ofthe connecting portion forms a curved bearing surface against which arod can bear.

In the system of the present invention the ware can be loaded as closelyas possible, so that for a given ware capacity, the belt can be drivenat a lower speed, thereby increasing the life of the belt. Also, therod-link arrangement allows the belt to be used in normal charge anddischarge operations, and about end pulleys, rolls and takeupmechanisms. Also, for a given inside radius of a lateral curve aboutwhich the belt travels, the tension on a belt of the present inventionin a spiral or curved tier system would be less than with conventionalrod-link belts.

The use of support links in accordance with the present invention,wherein the support links are used in combination with constant pitchU-shaped inside links, also results in significant advantages. Thesupport links allow for a significant reduction in height of theexternal belt support, while maintaining compatibility with sprocketsand allowing the belt to proceed about comparatively tight bends aroundrolls, pulleys, etc. Furthermore, these advantages are attained withoutthe disadvantages of the collapsing inner belt edge mentioned above,such as lower efficiency, wrinkling of ware or freezing together ofadjacent ware. A smoother transition from straight line conveying intohelical, stacked tier conveying also results from preventing thecollapse of the inner edge of the belt by the constant pitch U-shapedinside links.

Finally, the use of tractive links having work-hardened bearing surfacesgreatly enhances the wear characteristics of the tractive links. Thework-hardened, curved inner bearing surface of the connecting portion ofthe links reduces wear elongation of the links in two ways. First, byincreasing the area of contact, the same volume of wear would representa smaller elongation of the link pitch. Secondly, by forming the curvedsurface through a coining process which reduces the thickness of theconnecting portion from a relatively large thickness to a smallerthickness, the connecting portion becomes a work-hardened, wearresistant section of material. Prevention of wear elongation of tractivelinks is particularly important for the belt of the present inventionwherein the belt and conveyor system are designed so that the insidelinks remain tractive in both straight line and lateral curved motion,and, as the belt is frequently used in environments where sanitation isimportant, undesirable wear debris can be diminished.

Further objects, features and other aspects of this invention will beunderstood from the following detailed description of the preferredembodiment of this invention referring to the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a portion of a conveyor belt in accordance withthe present invention, illustrating the belt traveling in a straightline direction;

FIG. 2 is a plan view of the conveyor belt of FIG. 1, illustrating thebelt passing around a lateral curve;

FIG. 3 is a sectional view taken generally along lines 3--3 of FIG. 1;

FIG. 4 is a sectional view taken generally along line 4--4 of FIG. 1;

FIG. 5 is a plan view of an improved U-shaped link having awork-hardened, curved bearing surface and modified leg portions;

FIG. 6 is a side view of the link illustrated in FIG. 5;

FIG. 7 is a schematic plan view of a portion of a conveyor belt inaccordance with the present invention, using a second embodiment of alink mechanism and illustrating the belt passing around a lateral curve;

FIG. 8 is a schematic plan view of the conveyor belt of FIG. 7,illustrating the belt traveling in a straight line direction;

FIG. 9 is a side view of a dual pitch link in accordance with thepresent invention;

FIG. 10 is a sectional view taken generally along the line 10--10 ofFIG. 9;

FIG. 11 is a sectional view taken generally along the line 11--11 ofFIG. 9;

FIG. 12 is a schematic side view, illustrating another embodiment ofdual pitch links pivoting from a first pitch to a second greater pitch;

FIG. 13 is a schematic side view similar to FIG. 12, illustrating thedual pitch links pivoting form the second greater pitch to the firstshorter pitch;

FIG. 14 is an end view, partially in section, illustrating a guide tractfor receiving a rod end;

FIG. 15 is a schematic top plan view illustrating a conveyor beltdesigned to travel in both lateral directions with dual pitch links onboth transverse edges of the belt;

FIG. 16 is a side view of a support link in accordance with the presentinvention;

FIG. 17 is a front edge view of the support link illustrated in FIG. 16;

FIG. 18 is a top plan view of the support link illustrated in FIG. 16;

FIG. 19 is a schematic vertical sectional view illustrating a pair ofstacked tiers of a conveyor belt with the support links disposed alongthe inside edge of the belt;

FIG. 20 is a top plan view of a portion of the conveyor belt illustratedin FIG. 19;

FIG. 21 is a side view along the inside transverse edge of the conveyorbelt illustrated in FIG. 19;

FIG. 22 is a schematic drawing of a conveyor system in accordacne withthe present invention wherein the belt conveys about a helical path andis driven by a frictional drive mechanism; and

FIg. 23 is a schematic drawing of another embodiment of a conveyorsystem in accordance with the present invention wherein the conveyorbelt conveys about a helical path and is driven by a positive drivemechanism.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures wherein like numerals indicate like elements, aportion of a conveyor belt 10 is shown in FIGS. 1 and 2. FIG. 1illustrates the orientation of belt 10 as it moves in a straight lineconveying motion, and FIG. 2 illustrates the orientation of belt 10 asit moves in a lateral curved direction to the left. The left edge ofbelt 10 therefore can be described as the inside concave edge of belt10, while the right edge can be described as the outside convex edge ofbelt 10. Conveyor belt 10 is formed of a plurality of rods 12, whichextend transversely of the length of belt 10 between inside and outsideends, inside links 14 along the inside edge of belt 10 and outside links16 and 17 along the opposite, outside edge of belt 10. Links 14, 16 and17 couple adjacent rods 12 to one another to form a length of belt 10. Awoven mesh material 18 may be disposed around rods 12 and between links14 and 16. The ends of rods 12 have enlarged or upset ends. Insidemostlinks 14 are held in position by welding to the inside enlarged ends ofrod 12. The outermost inside links 14 and outside links 16 are likewiseheld in transverse position by being welded to rods 12.

Links 14 are generally U-shaped links having leg portions 20 whichextend generally in the lengthwise direction of belt 10, and connectingportions 22, which join leg portions 20. Leg portions 20 have a pair ofspaced holes 24, 25 for receiving the inside ends of a pair of rods 12.Holes 24, at the trailing end of link 14, are slightly oversized withrespect to the cross-sectional dimension of rod 12 to permit cleaning ofthe belt. Holes 25, at the leading end of links 14, are in the form of aslot of oversized width, likewise for the purpose of permittingcleaning. Holes 24 and 25 are located and shaped so that the inside endsof rods 12 are kept at a first pitch (center to center spacing betweenadjacent rods 12) when the belt is under tractive load. Also, links 14and rods 12 along the inside concave edge of belt 10 remain undertractive load during both straight line motion and lateral curvedmotion. As will be explained, the inside portions of rods 12 are kept atthe first pitch and under tractive load in both straight line motion andlateral curved motion of belt 10 by the specific design of thecombination of links 14, 16 and 17, which form a link mechanism for belt10.

Inside links 14 have leg portions 20 which are substantially straightand which diverge outwardly from opposite ends of connecting portion 22.Alternatively, the inside links can be configured as links 14', whichare also generally U-shaped and are illustrated in FIGS. 5 and 6. Link14' has a connecting portion 22' similar to connecting portion 22,however, leg portions 20' are formed different from leg portions 20.Each leg portion 20' includes an inner section 42 extending generallyperpendicularly from connecting portion 22', a middle section 44diverging outwardly from inner section 42, and an outer section 46extending from middle section 44 in a direction generally parallel toinner section 42.

Outside links 16 likewise each have a pair of spaced apart leg portions28 joined by a connecting portion 30. Leg portions 28, like leg portions20', include inner and outer sections 29 and 31, orientatedperpendicular to connecting portion 30, which are joined by a middleoutwardly diverging section 33 so that leg portions 28 take on a steppedconfiguration, gradually increasing in width away from connectingportion 30. Such a configuration is similar to prior art nestableU-shaped links. As seen in FIG. 3, each leg portion 28 has a pair ofholes 34, 35 for receiving adjacent rods 12. Hole 35, which is adjacentconnecting portion 30 is in the form of an elongate slot, which allowsrods 12 to move from the collapsed position shown in FIG. 1 duringstraight line conveying motion, to the expanded position shown in FIG.2, during conveying about lateral curves.

In addition to U-shaped links 16, bar links 17 can be disposed in asingle row along the outer transverse edge of belt 10 between outsidelinks 16 and the enlarged heads at the outer ends of rods 12. Similar tolinks 16, links 17 have a pair of holes, at least one of which isslotted to permit the expansion of the pitch of the outer edge of belt12.

Each link 14, 14' is formed of a substantially flat piece of metal. Theflat piece of metal has a first thickness T₁ along the top and bottomareas of connecting portions 22, 22' and along leg portions 20, 20'. Acurved bearing surface 126, 126' is formed in the inner surface ofconnecting portions 22, 22', while the outer surface remainssubstantially flat. Bearing surface 126, 126' is formed by a coiningprocess wherein the material of connecting portions 22, 22' iscompressed to a maximum reduced thickness T₂. The compressed, reducedthickness area thus becomes a work-hardened area of connecting portions22, 22'. The maximum reduced thickness T₂ is at least 90% of thicknessT₁ and not less than preferably 70%, with a typical example being T₁ of0.105 inch recuced to T₂ of 0.80 inch. The curved bearing surfacesubstantially mates with the outer surface of rod 12, i.e. hassubstantially the same radius of curvature. Links 16 can also include awork-hardened bearing surface. However, this is not necessary sincelinks 16 are designed not to take on any significant tractive load.

Conveyor belt 10 and links 14, 16 and 17 are designed to be used in aconveying system wherein belt 10 will travel about lateral curves in asingle direction and the lateral curves have a predetermined maximumcurvature, i.e., the radius of curvature of the tightest lateral curvein the system will not be below a predetermined value. Links 14, 16 and17 will have predetermined spacing between the forwardmost andrearwardmost surfaces of the holes in the links which is correlated tothe predetermined maximum curvature of the belt travel and to oneanother. This correlation of spacing is set to assure that the portionsof rods 12 along the inside edge of the belt remain at substantially thefirst pitch, and that at least one of the inside links 14, 14' continuesto bear a tractive load while the belt proceeds around lateral curves upto the predetermined maximum curvature.

Conveyor belt 10 is driven along its inside edge in a conventionalmanner by a drive sprocket or drive cage engaging the inside edge of thebelt. As the belt travels in a straight line direction, the tractiveload is shared by all the inside links, and the inside ends of the rodsare kept at the first pitch. The use of at least two inside U-shapedlinks assures that rods 12 extend substantially parallel during straightline motion under tractive load. If only one U-shaped link were usedalong the inside edge, the rode might extend in a non-parallel mannerdue to inaccuracies in the formation of the U-shape. It is thereforeimportant that a plurality of inside links be used to assure theparallel alignment of the rods.

As belt 10 travels about a lateral curve, the outside ends of rods 12expand in the slots of the outside links 16, 17 and the tractive loadgradually shifts to the inside links farthest from the inside edge ofthe belt. Links 14 have a first predetermined spacing between theforwardmost and rearwardmost surfaces of their holes, and outside links16 and 17 have a second, greater spacing between the forwardmost andrearwardmost surfaces of their holes. The first and second predeterminedspacings are correlated to one another and to the predetermined maximumcurvature of the belt so that outside links 16 and 17 assume only aminimal amount of the tractive load during travel about a lateral curveof the predetermined maximum curvature. Preferably, this predeterminedspacing results in rods 12 contacting the bearing surfaces of the holesin outside links 16 and/or 17 without assuming any measurable tractiveload so that inside links 14 continue to assume substantially all thetractive load. This condition is particularly desirable because links 16and 17 will allow only a negligible amount of play between links 16, 17and the bearing surfaces of rods 12, thereby assuring smoothness ofoperation, while also insuring that the inside links remain tractive andthe inside edge of the belt does not collapse. This is accomplished bysetting the ratio of the spacing (P_(o) ') of the holes in the outsidelinks 16, 17 to the distance (R_(o)) from the center of the radius ofcurvature of the belt to the outermost outside links in the tightestcurve only slightly greater than the ratio of the spacing (P_(i)) of theholes 24, 25 in the inside links 14 to the distance (R_(i)) from thecenter of the radius of curvature of the belt to the outermost leg 20 ofinside links 14. Using the equation: ##EQU1## then P_(o) '=P_(o) +0.005to 0.010 inches. For example, in a system with a four and a half (41/2)foot radius drive cage, two one-inch inside links, and a three (3) footwide belt: R_(i) =56 inches; R_(o) =90 inches; P_(i) =1.080 inches; andP_(o) =1.735 inches; then P_(o) '=1,740 to 1,745 inches. In such a belt,where the tractive load in the helical path could typically be 200pounds, the inside links would continue to assume 150 to 200 pounds ofthe tractive load in lateral curves of the predetermined maximumcurvature.

In addition, U-shaped outside links 16 serve an important function inpreventing the outer edge of belt 10 from lagging an unacceptable amountbehind the perfect radial extension of rod 12 from inner links 14. Suchlagging is a result of a drag force created by the weight of belt 10 andits associated product load on a support surface as the belt moves abouta lateral curve. In order for the rods to lag, links 16 would have torotate with respect to a perfect radial line of the rods in a curvedpath; however, such rotation is held to a minimum by the nesting actionof consecutive U-shaped outside links 16, thereby restricting the amountof lag that can occur. For manufacturing ease, when U-shaped links 16are used in combination with bar links 17, bar links 17 can be designedto have the correlated spacing P_(o) ' and links 16 can have an evengreater longitudinal spacing between the end surfaces of their holes,thereby functioning principally to prevent lag.

Referring to the FIGS. 7-15, a second embodiment of a conveyor belt,designated generally 10a is illustrated. A portion of a conveyor belt10a is shown in FIGS. 7 and 8. Conveyor belt 10a is formed of aplurality of rods 12a, single pitch links 14a along one edge of belt 10and dual pitch links 16a along the opposite edge of belt 10. Rods 12aextend transversely of the length of belt 10a and they have enlarged orupset ends. Links 14a and 16a couple adjacent rods 12a to one another toform a length of belt 10a.

Single pitch links 14a can be conventional U-shaped links havingapertures for receiving the inside ends of a pair of rods 12. Theapertures in links 14a are slightly oversized with respect to thecross-sectional dimension of rods 12a to permit cleaning, nevertheless,links 14a hold the ends of rods 12a to substantially a constant orsingle pitch. Alternatively links 14a can be formed with work-hardenedbearing surface as in links 14 and 14' or can take on the configurationof links 14'.

Links 16a are dual pitch links designed to change the pitch of rods 12a(spacing between adjacent rods 12a) along the edge at which they aredisposed between a first pitch and a second greater pitch. The firstpitch is substantially equal to the pitch at which links 14a hold theinside ends of rods 12a during straight line motion as shown in FIG. 8.When belt 10a proceeds around a lateral curve, as shown in FIG. 7, dualpitch links 16a move the outside ends of the rods to which they arecoupled to the second greater pitch along the outside convex edge of thelateral curve, while links 14a hold the inside ends of the rods to whichthey are attached to the first pitch along the inside concave edge ofthe lateral curve. As with rods 12, the inside PG,17 portions of rods12a are kept at substantially the first pitch and under tractive load inboth straight line motion and lateral curved motion of belt 10a by thespecific design of the combination of single pitch links 14a and dualpitch links 16a, which form a link mechanism for belt 10a.

FIG. 9 illustrates the stuctural details of one embodiment of a dualpitch link 16a. Link 16a is preferably formed as a single integral body180 which has a generally triangular shape or perimeter. A pivotaperture 200 and an elongate pitch changing slot 220 are formed throughbody 180 of dual pitch link 16a. As further illustrated in FIGS. 10 and11, body 180 can be formed of two thicknesses of material, i.e., a thickportion 240 extending around a substantial portion of aperture 200 andslot 220, and a thinner web portion 260 filling in and extending aroundthe border of thicker portion 240. A two thickness configuration of body180 is particularly suitable for a body 180 formed of a molded plasticmaterial wherein a sturdy border is provided for aperture 200 and slot220, while the thinner web portions 260 form an easy to handle,structurally sound and material saving configuration for the integralbody 180.

FIGS. 12 and 13 illustrate an alternate, simplified configuration forthe body of dual pitch links 16a, identified as body 180'. As seentherein, body 180' is formed of a flat piece of material containingaperture 200 and slot 220. The shape of body 180' is particularlysuitable for links 16a made from machined metal.

Referring to FIGS. 7, 8, 12 and 13, operation of belt 10a will beexplained. FIG. 8 illustrates belt 10a proceeding in a straight linedirection indicated by arrow A. As seen therein, the pitch is the sameat both edges of belt 10a. Links 14a are single pitch links which holdadjacent rods at this constant pitch. The position of adjacent rods instraight line conveying is illustrated in FIG. 12 by the left-most pairof rods 12a, and the three right-most rods in FIG. 13. Referring to FIG.12, a first rod 12a is received in pivot aperture 200 of the left-mostdual pitch link 16a and an adjacent rod 12a is received in pitchchanging slot 220 of this link 16a. The last-mentioned rod 12a islocated in a first pitch area 280 of slot 220 which is located adjacentrods 12a at substantially the same pitch as links 14a locate theadjacent rods. This pitch is the shortest pitch allowed by link 16a. Inthis condition, tractive load can be shared between the U-shaped singlepitch links 14a and the dual pitch links 16a. Links 14a and 16a can bedimensioned, however, so that the relative amounts of tractive load canbe shared unevenly. For example, when dual pitch links 16a are formed ofa plastic material, it is desirable to have single pitch links 14a,which are generally formed of metal, carry more of the tractive load.

The orientation of rods 12a, when belt 10a proceeds around a lateralcurve, as shown by arrow B, is illustrated in FIG. 7. As seen therein,the inside concave edge of belt 10a remains at the same first pitch asin straight line motion, while the outside convex edge of belt 10a hasbeen moved to a greater pitch by dual pitch links 16a. FIG. 12illustrates the pivoting motion of links 16a that moves the outside endsof rods 12a along the outside edge to the second greater pitch. As seentherein, a cam surface or the like 340 for pivoting the dual pitch linksis located adjacent outside edge of belt 10a in alignment with links16a. As belt 10a proceeds in the direction of arrow C, an upper edge oflinks 16a contacts cam surface 340 which causes links 16a to pivot in acounterclockwise direction. The pivoting motion of links 16a causes theends of rods 12a received in the pitch changing slot 220 to slide fromthe first pitch area 280, wherein adjacent rods 12a are close to oneanother, to a second pitch area 360 where the spacing between adjacentrods 12a is greater. The pitch changing slot second pitch areaforwardmost end surface is 370. See also, FIG. 9. As seen in FIG. 12,cam surface 340 can cause link 16a to pivot 90° and locate rod 12acarried in slot 220 at the furthest end of slot 220 to contact thesecond pitch area 360 end surface 370. The length and orientation ofpitch changing slot 220 is selected to accommodate the greatest pitchalong outside curve edge for a given system. Of course, if smallerpitches are required within the same system, cam suface 340 can bedesigned to pivot dual pitch links 16a to a lesser degree, therebylocating the end of rod 12a received in slot 220 within an intermediateposition in second pitch area 360.

FIG. 13 illustrates the manner in which links 16a are pivoted to returnrods 12a from the second pitch used in lateral curved motion to thefirst pitch used in straight line conveying. As shown therein, belt 10aproceeds in the direction of arrow D and links 16a contact a cam surfaceor the like 380, which pivots links 16a in a clockwise direction. Theclockwise pivoting motion of links 16a moves the ends of transverse rods12a from the second pitch area 360 to the first pitch area 280 of pitchchanging slots 220.

As seen in FIG. 14, an elongate guide block 400, having a guide slot420, can be located adjacent the belt outer edge in the transition areawhere cam surfaces 340 and 380 cause pivoting motion of links 16a. Theoutermost end of rods 12a are carried within guide slot 420 to keep theends of rods 12a within the plane of conveying motion of belt 10a duringpivoting of links 16a. As further seen in FIG. 14, the ends of rods 12areceived within slot 420 preferably have a double struck upset head,which assures that the end of transverse rod 12a remains within guideslot 420 even after wear occurs. Guide slot 420 can be eliminated atcurves where smooth travel of the belt is not required, for example, onreturn portions of the conveyor where no ware is being transported, oron a loaded portion of the conveyor if a slight momentary humping of theconveyor suface will not disarrange the ware.

Similar to conveyor belt 10 and links 14, 16 and 17, conveyor belt 10aand links 14a and 16a can be used in a conveying system embodimentwherein belt 10a will travel about lateral curves in a single directionand the lateral curves have a predetermined maximum curvature, i.e., theradius of curvature of the tightest lateral curve in the system will notbe below a predetermined value. Single pitch links 14a and dual pitchlinks 16a will have predetermined spacing between the forwardmost andrearwardmost surfaces of the holes or slots in the links which arecorrelated to the predetermined maximum curvature of the belt travel andto one another. This correlation of spacing is set to assure that theportions of rods 12a along the inside edge of the belt remain atsubstantially the first pitch, and that at least one of the insidesingle pitch links continues to bear a tractive load while the beltproceeds around lateral curves up to the predetermined maximumcurvature. This correlation of spacing is set in the same manner asdiscussed above with respect to belt 10.

Conveyor belt 10a, also similar to conveyor belt 10, is driven along itsinside edge in a conventional manner by a drive sprocket or drive cageengaging the inside edge of the belt. As the belt travels in a straightline direction, the tractive load is normally shared by all the singlepitch links 14a, and the inside ends of the rods are kept at the firstpitch. The use of at least two inside U-shaped links helps assure thatrods 12a extend substantially parallel during straight line motion undertractive load.

As belt 10a travels about a lateral curve, the outside ends of rods 12aexpand in the pitch changing slots 220 of the dual pitch links 16a. Therod actually expands from the slot first pitch area 280 to the secondpitch area 360. Also, the tractive load gradually shifts to one of thetwo single pitch links which is farthest from the inside edge of thebelt.

FIG. 15 illustrates an embodiment of belt 10a wherein a conveyor systemuses dual pitch links 16a disposed along both sides of the belt in orderto allow the belt to travel in both the left and right directions asshown by arrows E and F. In such motion, the dual pitch links on theinside edge of the curve would remain at the first pitch position, whiledual pitch links 16a along the outside edge of the curve would bepivoted to the second, greater pitch orientation. FIG. 15 alsoillustrates belt 10a as part of a conveying system with a conventionalconveyor drive mechanism 460, such as a sprocket drive, for moving theconveyor belt 12a.

A mesh overlay 480 placed around rods 12a is also illustrated in FIG.15. Mesh overlay 480 can be of any conventional design, such as wireformed into flattened helicals. The overlay is used to provide supportfor relatively easily damaged ware. The overlay can be manufactured to awidth somewhat wider than its final assembled form on belt 10a so thatit provides pressure in the transverse direction against both the innerand outer links to assure that they maintain their transverse posittionon rods 12a, thereby eliminating the need for further welding or the useof mechanical devices to hold the links in place.

FIGS. 19, 20, and 21 illustrate an embodiment of the invention wherein aconveyor belt 10' is used in a conveying system in which belt 10'travels along a helical path comprised of a number of superimposedhelically extending tiers. The conveyor belt of this embodiment will bedesignated 10', with elements of belt 10' which are similar to belt 10indicated by like primed numerals. FIGS. 16, 17 and 18 illustratedetails of an inside support link 40 used with belt 10'.

Support links 40 include a longitudinal portion 48 and tab portions 50.Longitudinal portion 48 is formed in two sections, i.e., a lower section49 and an upper section 51. Lower section 49 contains a pair of holes 55for receiving ends of adjacent rods 12', and tab portions 50 extend inopposite transverse directions from an upper end of upper section 51.Upper section 51 extends both upward and longitudinally in twodirections from lower section 49. As best seen in FIG. 21, a firstsupport link 40A is coupled to a first pair of adjacent rods 12A', whilethe next support link 40B is coupled to the next separate pair ofadjacent rods 12B'. Lower section 49 is held in alignment with thedirection of travel of belt 10' by end sections 46 of U-shaped links14'. Upper section 51 of support links 40 are angularly offset byapproximately 4 degrees from the respective lower sections 49 in orderto allow the longitudinal ends of adjacent longitudinal portions 51 tooverlap. One end of longitudinal portions 51 include dimples 53 whichkeep the overlapping portions of adjacent support links 40 out ofcontact to permit cleaning.

Each tab portion 50 has a width which is sufficient to contact andsupport links 14' disposed in a tier above it. Also, the length of eachtab portion 50 is set so that belt 10' can proceed around reverse bendswithout adjacent tab portions 50 coming into contact with one another.

As seen in FIG. 19, as the belt proceeds around a helical path, theouter ends of belt 10 are supported by an independent support structure60. Support structure 60 includes a plurality of vertical members 62(one of which is illustrated), from which a plurality of horizontal tiersupports 64 extend. Each tier support 64 includes a low friction bearingmaterial 66 on which outer links 16' slide. The inside edge of belt 10'is supported on a rotating base (not shown) and successive tiers of thehelical path created by belt 10' are supported one upon another by meansof support links 40. To accomplish this self-supporting feature, thevertical distance which tab portions 50 are located above rods 12' isselected to accommodate the particular helical path and the ware to besupported on belt 10'. Belt 10' is driven by an internal rotating cagewhich includes a plurality of vertically extending driving members 70.FIG. 19 illustrates belt 10' with generally U-shaped outside link 16'and bar links 17'. However, belt 10' can also incorporate dual pitchlinks 16a along the outside edge of belt 10'.

Referring now to FIG. 22 a spiral low tension conveying system 100 ofthe type shown in U.S. Pat. Nos. 4,078,655 and 3,348,659 is illustrated.System 100, can incorporate either of the belts 10, 10' or 10a of thepresent invention. Since the low tension system is fully described inthese patents, which are herein incorporated by reference, and suchhelical conveying systems are known in the art only a brief descriptionwill be given here. In such a low tension system 100, a cage typedriving drum 102 frictionally engages the inner edge of belt 10 (10',10a) to drive it with relatively low tension through a helical patharound the drum. In addition, a positive sprocket drive 104 engages thebelt 10 along a straight portion thereof. A motor 105 drives the drum102 through gearing 106 and also drives the positive sprocket drive 104through interconnected gearing 107. The belt 10 travels from thesprocket drive 104, past weighted tension take up roller 110 and idlerpulleys 111 to a straight loading portion 108, then in helical loopsaround the drum 102 to a straight discharge portion 109 and aroundanother idler 111 back to the drive sprocket.

Referring now to FIG. 23 a spiral view low tension conveying systems 200of the type shown in U.S. Pat. No. 4,741,430, issued on May 3, 1988 toGerald C. Roinestad is illustrated. System 201 can incorporate either ofthe belts 10, 10' or 10a of the present invention. Since the very lowtension system is fully described in that patent application, which isherein incorporated by reference, and such helical conveying systems areknown in the art only a brief description will be given here. In such asystem 201, a cage type drivingg drum 202 positively engages the inneredge of belt 10 (10', 10a) to drive it with very low tension through ahelical path around the drum. Driving drum 202 functions as the primarydrive for the belt moving in the helical path; however, secondary drives204 and 206 are provided adjacent the inlet and outlet of the helicalpath to maintain a desired fixed length of the belt in the helical path.

Belts 10 and 10' are particularly suited for use in systems 100 and 201.The maximum curvature of the system is located in the helical path andthe spacing between the openings in links 14, 16, 17 (and 40, if used),or between 14a and 16a, is correlated to the radius of curvature of thehelical path. This assures non-collapse of the inner edge of the beltwithin the helical path, while at the same time assuring smoothoperation of the belt along its outer edge.

This invention has been described in detail in connection with theillustrated preferred embodiments. These embodiments, however, aremerely for example only and the invention is not restricted thereto. Itwill be easily understood by those skilled in the art that othervariations and modifications can be easily made within the scope of thisinvention, as defined by the appended claims.

We claim:
 1. A conveyor belt for conveying in both a straight linedirection and around lateral curves in a single direction, the lateralcurves having a predetermined maximum curvature with a predeterminedradius of curvature, the conveyor belt comprising a plurality of rodsand connecting means for connecting said rods to form a length of thebelt, said rods extending transversely of the length of the belt betweenan inside end along the inside edge of the lateral curves and an outsideend along the outside edge of the lateral curves, said rods beingarranged adjacent one another longitudinally along the length of thebelt, said connecting means including link means disposed adjacent saidinside and outside ends of said rods for coupling adjacent pairs of saidrods to one another, said link means including, along the inside concaveedge of the belt, at least two generally U-shaped inside links joiningthe inside ends of each pair of adjacent rods and, along the outsideconvex edge of the belt, at least one outside link joining the outsideends of each pair of adjacent rods, said generally U-shaped inside linkseach having a pair of spaced leg portions joined by a connectingportion, each of said leg portions having holes for receiving said rods,each of said outside links having holes for receiving said rods, saidholes in the legs of said inside links having end surfaces with a firstpredetermined longitudinal spacing, said holes in said outside linkshaving end surfaces with a second predetermined longitudinal spacing,said first and second longitudinal spacings being correlated to oneanother and to the predetermined radius of curvature so that in straightline conveying motion the inside ends of said rods are kept at a firstpitch and the U-shaped inside links are tractive while the outside linksare non-tractive, and during lateral curved conveying motion the insideends of said rods are kept at substantially the first pitch and at leastone of said U-shaped inside links remains tractive while the outsideends of said rods move to a second greater pitch.
 2. A conveyor belt inaccordance with claim 1 including at least one support link disposedadjacent said inside links and coupled between pairs of said adjacentrods, said support links including a longitudinal portion extending bothlongitudinally between a pair of said adjacent rods and vertically awayfrom said rods and at least one tab portion extending transversely fromsaid longitudinal portion, holes being formed in said longitudinalportion through which an adjacent pair of rods extend, said tab portionsbeing spaced a predetermined vertical distance from said rods to contactand support an inside edge of an adjacent vertically spaced tier of saidbelt when said belt is arranged to travel along a helical conveyingpath.
 3. A conveyor belt in accordance with claim 2 wherein said spacedleg portions of said U-shaped inside links have end sections adjacent tothe longitidinal portions of said support links, and said end sectionsextending substantially perpendicular to the transverse extent of saidrods to align said support links with respect to said rods.
 4. Aconveyor belt in accordance with claim 1 wherein said outside linksinclude at least one bar link and have holes for receiving and couplingadjacent pairs of said rods.
 5. A conveyor belt in accordance with claim1 wherein said connecting portion of each of said U-shaped inside linkshas a work-hardened bearing surface.
 6. A conveyor belt in accordancewith claim 1 wherein the correlation between the longitudinally spacedend surfaces of the holes in said inside and outside links causes theoutside ends of said rods to contact the opposing end surfaces in theholes of said outside links when the belt travels about a lateral curveof the predetermined maximum curvature with the outside links assuming aminimal amount of tractive load to assure that at least one of saidinside links remains tractive and the inside ends of said rods remain atsubstantially the first pitch.
 7. A conveyor belt in accordance withclaim 6 wherein the ratio of the predetermined spacing between the holesof said outside links to the distance from the center of the saidpredetermined radius of curvature to the outermost outside links is onlyslightly greater than the ratio of the predetermined spacing between theholes in said inside links to the distance from the center of thepredetermined radius of curvature to the outermost leg of said insidelinks.
 8. A conveyor belt for conveying in both a straight linedirection and around lateral curves in a single direction, the lateralcurves including a helical path and having a predetermined maximumcurvature with a predetermined radius of curvature in the helical path,the belt comprising a plurality of rods and connecting means forconnecting said rods to form a length of the belt, said rods extendingtransversely of the length of the belt between an inside end along theinside edge of the lateral curves and an outside end along the outsideedge of the lateral curves, said rods being arranged adjacent oneanother longitudinally along the length of the belt, said connectingmeans including link means disposed adjacent said inside and outsideends of said rods for coupling adjacent pairs of said rods to oneanother, said link means including at least two generally U-shapedinside links and a support link disposed along the inside edge of saidbelt, and at least one outside link disposed along the outside edge ofthe belt, said inside U-shaped links each having a pair of spaced legportions connected by a connecting portion, each of said leg portionshaving holes for receiving adjacent ones of said rods, each of saidoutside links having holes for receiving adjacent ones of said rods,said support links having a longitudinal portion extending bothlongitudinally between a pair of said adjacent rods and vertically awayfrom said rods and at least one tab portion extending transversely fromsaid longitudinal portion, said tab portion being spaced a predeterminedvertical distance from said rods to contact and support an inside edgeof an adjacent vertically spaced tier of said belt when said belttravels along the helical path, said longitudinal portion of saidsupport links having holes for receiving adjacent ones of said rods,said holes formed in said inside links having end surfaces with a firstpredetermined longitudinal spacing, said holes formed in said outsidelinks having a second predetermined longitudinal spacing, said first andsecond longitudinal spacings being correlated to one another and to thepredetermined radius of curvature such that in straight line conveyingmotion the inside ends of said rods are kept at a first pitch and theinside U-shaped links are tractive while the outside links arenon-tractive, and during lateral curved conveying motion the inside endsof said rods are kept at substantially the first pitch and at least oneof the inside U-shaped links remains tractive while the outside ends ofthe rods move to a second greater pitch.
 9. A conveyor belt inaccordance with claim 8 wherein said outside links include at least onebar link having holes with said correlated predetermined second endsurface spacing for receiving and coupling adjacent pairs of said rods.10. A conveyor belt in accordance with claim 8 wherein each of saidsupport links is disposed between a pair of said U-shaped inside links,said spaced leg portions of said U-shaped inside links have end sectionsadjacent to the longitudinal portions of said support links, and saidend sections extending substantially perpendicular to the transverseextent of said rods to align the support links with respect to saidrods.
 11. A conveyor belt in accordance with claim 8 or 10 wherein saidlongitudinal portion of each of said support links has a lower sectionwith said holes for coupling to said rods and an upper section extendingvertically and longitudinally from the lower section, said upper sectionbeing angularly offset from the lower section and having a longitudinaldimension such that the upper sections of adjacent support links overlapone another.
 12. In a conveying system including a conveyor belt and adrive means for moving the belt along a conveying path, said systemorientating the belt in both a straight line direction and aroundlateral curves in a single direction, the later curves including ahelical portion forming a plurality of stacked tiers of the belt, andhaving a predetermined maximum curvature with a predetermined radius ofcurvature in the helical portion, the belt comprising a plurality ofrods and connecting means for connecting said rods to form a length ofthe belt, said rods extending transversely of the length of the beltbetween an inside end along the inside edge of the lateral curves and anoutside end along the outside edge of the lateral curves, said rodsbeing arranged adjacent one another longitudinally along the length ofthe belt, said connecting means including link means disposed adjacentsaid inside and outside ends of said rods for coupling adjacent pairs ofsaid rods to one another, said link means including, along the insideconcave edge of the belt, at least two generally U-shaped inside linksjoining the inside ends of each pair of adjacent rods, and, along theoutside edge of the belt at least one link joining the outside ends ofeach pair of adjacent rods, said generally U-shaped inside links eachhaving a pair of spaced leg portions joined by a connecting portion,each of said leg portions having holes for receiving said rods, each ofsaid outside links having holes for receiving said rods, said holes inthe legs of said inside links having end surfaces with a firstpredetermined longitudinal spacing, said holes in said outside linkshaving end surfaces with a second predetermined longitudinal spacing,said first and second longitudinal spacings being correlated to oneanother and to the predetermined radius of curvature so that in straightline conveying motion the inside ends of said rods are kept at a firstpitch and the U-shaped inside links are tractive while the outside linksare non-tractive, and during lateral curved conveying motion the insideends of said rods are kept at substantially the first pitch and at leastone of the U-shaped inside links remains tractive while the outside endsof said rods move to a second greater pitch.
 13. In a conveying systemin accordance with claim 12 wherein said outside links include at leastone bar link having holes with said second predetermined correlated endsurface spacing for receiving and coupling adjacent pairs of said rods.14. In a conveying system in accordance with claim 12 including at leastone support link disposed adjacent said inside links and coupled betweenadjacent pairs of said rods, said support links having tab portionsspaced a predetermined distance from said rods to contact and supportthe inside edge of a superimposed verical tier of said belt.
 15. In aconveying system in accordance with claim 12 wherein said drive meansincludes a rotating driving member frictionally engaging the inside edgeof said belt in the helical portion.
 16. In a conveying system inaccordance with claim 12 wherein said drive means includes a rotatingdriving member positively engaging the inside edge of said belt in thehelical portion.